We propose a novel therapeutic strategy to combat pancreatic cancer by targeting the cell surface glucose regulated protein GRP78 (sGRP78), a stress-inducible master chaperone which is actively promoted to the cell surface upon endoplasmic reticulum (ER) stress in cancer cells, while sparing normal organs. Pancreatic ductal adenocarcinoma (PDAC) is one of deadliest of all cancers with a 5 yr survival rate of <5%, thus there is an urgent need for developing an efficacious therapy for PDAC. This proposal is based on emerging evidence from our laboratory and others that in pancreatic cancer GRP78 is prominently expressed in both human and murine pre-invasive and PDAC lesions and sGRP78 co-localizes with activated AKT at the cell surface of PDAC. We have recently discovered a highly specific and potent monoclonal antibody, MAb159, that targets sGRP78 leading to endocytosis, inhibition of the PI3K/AKT pathway, and tumor cell death by inducing apoptosis. Our hypothesis is that pancreatic cancer characterized by a dense stroma is subjected to an adverse microenvironment resulting in hypoxia and nutrient deprivation. This coupled with intrinsic high proliferation and altered metabolism, creates ER stress in the cancer cells leading to GRP78 upregulation and active promotion of GRP78 surface localization as a major pro-survival response. Targeting sGRP78 with MAb159 induces endocytosis and degradation of sGRP78 complex at the cell surface, thereby offering a novel approach to blunt AKT and potentially other oncogenic pathways to suppress tumor growth and synergize with existing therapy in pancreatic cancer. Additionally, MAb159 treatment induces caspase-8 activation, indicative of activation of extrinsic cell death. Aim 1 will determine the mechanisms o action of MAb159 in human PDAC, addressing the requirement of endocytosis, AKT activation, the interactions between sGRP78 and the death-inducing signaling complex and synergy with gemcitabine. Based on our exciting preliminary data that MAb159 not only inhibits but can regress xenograft growth of human PDAC, Aim 2 will test the efficacy of MAb159, alone or in combination therapy, in the Pdx-1Cre; KrasG12D; p53f/+ (PKC) endogenous mouse pancreatic cancer model which recapitulates many of the features of human pancreatic cancer and offers a most vigorous test for agent efficacy. In parallel, the efficacy of MAb159 will be tested in orthotopic transplantation models of human PDAC with complex genetic alterations. In summary, this proposal tests two new concepts: 1) sGRP78 promotes tumor proliferation and survival in part through regulation of the PI3K/AKT pathway and the death-inducing signaling complex in PDAC, and 2) a novel therapeutic agent (MAb159 targeting sGRP78) may reverse tumor growth and resistance while sparing normal cells. The results of this study can be readily applied to other highly malignant and resistant tumors expressing sGRP78 and translatable to the clinic.